Field of the Disclosure
The present disclosure relates to a liquid crystal display (LCD) device, and more particularly, to a polarization layer having improved polarization degree and optical efficiency and an LCD device including the same.
Description of the Background
Recently, flat panel display (FPD) devices having lightweight and thin profile have been researched instead of a cathode ray tube (CRT).
Among the FPD devices, a liquid crystal display (LCD) device uses optical anisotropy of liquid crystal molecules to display images and has characteristics of high resolution, high image quality and being adequate to display a color image. As a result, the LCD device is widely used for desktops or monitors.
The LCD device may include a color filter substrate, an array substrate and a liquid crystal (LC) layer therebweeen.
FIG. 1 is an exploded perspective view of the related art LCD device, and FIG. 2 is a cross-sectional view of the related art LCD device.
Referring to FIGS. 1 and 2, the LCD device 1 includes a color filter substrate 20, an array substrate 10, an LC layer 30 between the color filter substrate 20 and the array substrate 10 and a backlight unit 40 under the array substrate 10.
On the color filter substrate 20, a black matrix BM having a lattice shape and blocking light, a color filter layer 23, which includes red, green and blue color filter patterns 23a, 23b and 23c, in openings of the black matrix BM and a transparent common electrode 28 are formed.
On the array substrate 10, a gate line 16, a data line 17, a thin film transistor (TFT) T as a switching element and a pixel electrode 18 in a pixel region P are formed. The gate line 16 and the data line 17 cross each other and define the pixel region P, and the TFT T is formed at each crossing portion of the gate and data lines 16 and 17.
The backlight unit 40 may include a light guide plate 41, a light source 45 at a side of the light guide plate 41, a reflective plate 42 under the light guide plate 41 and an optical sheet 43 between the light guide plate 41 and the array substrate 10.
The color filter substrate 20 and the array substrate 10 are attached with a sealant (not shown) at a periphery of a display region such that a liquid crystal (LC) panel is provided.
The color filter layer 23 includes dye or pigment such that pre-determined light is transmitted through the color filter layer 23 and the others are absorbed by the color filter layer 23. As a result, the LCD device 1 displays a color image. Since only one of red, green blue colors is transmitted through the color filter pattern 23a in one pixel region P, the transmittance of the color filter layer 23 may be less about 30% such that the optical efficiency of the LCD device 1 is decreased.
In addition, polarization plates 11 and 21 are disposed at outer sides of the array substrate and the color filter substrate 20. For example, iodine or dichroic dye is absorbed into a polyvinylalcohol (PVA) film and the PVA film is stretched along a pre-determined direction to form the polarization plates 11 and 21. The polarization plates 11 and 21 may have weak mechanical strength in the pre-determined direction. The polarization plates 11 and 21 may be contracted by heat or moisture such that the polarization degree of the polarization plates 11 and 21 may be decreased. In addition, since the light vibrating in a pre-determined direction is transmitted through the polarization plate, the efficiency of the polarization plate is less than 50%. Accordingly, the polarization plate is an important element affecting the optical efficiency and the brightness of the LCD device.
Moreover, since an alignment layer determining an initial arrangement of the LC molecule is formed between each of the color filter substrate 20 and the array substrate 10 and the LC layer 30, the fabrication process of the LCD device becomes complicated and the production cost of the LCD device is increased.